This invention relates generally to optically-based methods and apparatus for performing sorting, coding and authentication of objects, such as paper or polymer based objects including currency, checks, negotiable instruments, passports, wills and other documents.
In U.S. Pat. No. 5,448,582, issued Sep. 5, 1995, entitled xe2x80x9cOptical Sources Having a Strongly Scattering Gain Medium Providing Laser-Like Actionxe2x80x9d, the inventor disclosed a multi-phase gain medium including an emission phase (such as dye molecules) and a scattering phase (such as TiO2). A third, matrix phase may also be provided in some embodiments. Suitable materials for the matrix phase include solvents, glasses and polymers. The gain medium is shown to provide a laser-like spectral linewidth collapse above a certain pump pulse energy. The gain medium is disclosed to be suitable for encoding objects with multiple-wavelength codes, and to be suitable for use with a number of substrate materials, including polymers and textiles.
It is well known in the art to use various security techniques in an attempt to provide paper and other printable substrates that can be readily authenticated. Once the paper is authenticated, then the document or instrument printed on the paper may be assumed to be authentic as well, or at least to have passed a threshold test of authenticity. Watermarks, holograms, color changing inks and the like have all be used in the past. One well known technique places security threads in paper to hinder a non-authorized production of the paper or to authenticate already manufactured paper and/or a document or currency printed on the paper. Reference in this regard can be had to the following U.S. Patent U.S. Pat. No. 5,486,022, xe2x80x9cSecurity Threads Having At Least Two Security Detection Features and Security Papers Employing Samexe2x80x9d, by T. T. Crane; U.S. Pat. No. 4,534,398, xe2x80x9cSecurity Paperxe2x80x9d, by T. T. Crane; and U.S. Pat. No. 4,437,935, xe2x80x9cMethod and Apparatus for Providing Security Features in Paperxe2x80x9d, by F. G. Crane, Jr.
In addition to the problem of authentication, other problems arise with the use of currency, documents, and other pliable substrates (e.g. textiles) such as when using automatic sorting and counting machines. In such applications the sorting and/or counting machine should be able to accurately distinguish between different denomination notes, while doing so in a real time environment where the notes are moving at a relatively high velocity.
A problem also arises during a conventional use of fluorescent or phosphorescent materials. This problem is related to the saturation behavior of the optical output that is typical of these materials. Due to this saturation behavior the signal to noise properties of the output are degraded, especially for non-contact substrate processing.
A very advantageous solution to the various problems discussed above would be to provide a security structure that could be incorporated into the matrix that forms the document, currency, negotiable instrument, etc., wherein the structure could function to both authenticate the substrate as well as to enhance the countability and/or sortability of the substrate. The security structure should be small so that it can incorporated into substrates, low cost, and exhibit non-saturating or substantially non-saturating behavior that provides the structure with a high signal to noise output and a capability of being used in a non-contact, high speed mode of operation. An optically-based security structure in accordance with the teachings of this invention would enable such a non-contact, high speed mode of operation.
It is thus a first object and advantage of this invention to provide an improved optically based method and apparatus for authenticating objects, and possibly also counting and sorting objects, such as documents, currency, negotiable instruments, and other substrates that contain indicia.
It is another object and advantage of this invention to provide an optically-based security structure that can be used in thin substrate materials, such as sheet-like substrate materials based on paper or polymer.
It is a further object and advantage of this invention to provide a document or document substrate, such as paper or a polymer, that is printed and/or constructed so as enable the document or substrate to be accurately and unambiguously authenticated as being genuine, as well as to have enhanced counting and sorting properties.
It is another object and advantage of this invention to provide a mode or amplified spontaneous emission (ASE) structure that allows for the circumvention of the conventional output saturation behavior that is typical of conventional fluorescent or phosphorescent materials, thereby greatly enhancing the signal to noise properties of the output from the substrate and allowing for highly improved and robust non-contact processing.
It is one further object and advantage of this invention to provide an amplified spontaneous emission (ASE) structure in homogeneously or inhomogeneously broadened medium allowing for highly improved and robust non-contact processing of substrates, such as those that comprise currency and other documents.
The foregoing and other problems are overcome and the objects and advantages of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
Disclosed herein are methods and apparatus for at least one of authenticating, sorting or counting documents, as well as security structures contained within documents. The apparatus includes a laser or some other light source for illuminating all or a portion of a document. The document includes a substrate and at least one security structure or device located in or on the substrate.
In accordance with the teachings of this invention the security structure includes, in one embodiment, a gain medium coupled to a structure that supports the creation of at least one mode for electromagnetic radiation.
Further in accordance with the teachings of this invention the security structure includes, in another embodiment, a gain medium coupled to a structure having a dimension or length in one or more directions to produce and support amplified spontaneous emission (ASE).
A security device in accordance with this invention has a structure with boundaries whose geometry and material properties (e.g., index of refraction) support an enhancement of electromagnetic radiation that may be emitted from a gain medium, such as a dye and/or semiconductor particles, that is also contained within the device. The structure may be provided so as to favor the creation of at least one mode so as to enhance electromagnetic radiation within a narrow band of wavelengths. Suitable shapes for the structure include, but are not limited to, elongated generally cylindrical shapes such as filaments, spheres, half-spheres, toroids, cubes and other polyhedral shapes, as well as disks. The structures may be monolithic structures or multi-layered structures, or a combination of same. Preferably the security devices containing the structures are of a size compatible with the dimensions of the substrate or carrier into which they are placed, such as paper or thin polymer sheets such as those used for credit cards, debit cards and identification cards, such as driver""s licenses.
A laser source may output light having wavelengths that are predetermined to excite the gain medium. Apparatus that comprises the laser further includes at least one photodetector, or an array of photodetectors, that is responsive to at least one predetermined wavelength, and decision logic for at least one of indicating the authenticity of a document containing the security device, for counting the document, or for sorting the document. The decision logic operates based at least in part on a detection of the at least one predetermined wavelength or on the absence of at least one predetermined wavelength. In addition, the decision process for authentication may include the linewidth and other spectral features of the signature, such as its derivative. These parameters may be employed to further corroborate the presence of a lasing emission signature.
As employed herein a document could be a currency, or a passport, or a lottery ticket, or a negotiable security, or a credit card or a debit card, or an identification card such as a driver""s license or employee""s badge, or any substrate or carrier which it is desired to authenticate, count, encode with information, sort and/or verify.